I have 3 15" AOC USB Displaylink LCD Monitors.
I also have a Sunix VGA 2728 USB3 to DVI adapter.
Your drivers and their drivers will not coexist together on the same W7 Computer.
Even if they're not plugged in simultaneously, installing the one driver removes/breaks the other.
www.sunix.com.tw/services/driver.html?k=VGA2728